Right-click a boat to ride it. Then type "/tp @e[type=Boat,c=1] ~ ~8 ~". It will kick you out of the boat and teleport the boat up, leaving you dismounted on the ground.
Comments
I'm also unable to reproduce in 16w32b.
Awesome! So the bug got randomly fixed outside of notice. xD Nice.
Unable to reproduce in 16w32b. Can you reproduce it in 16w32b?